DSSC is represented by a photoelectrochemical solar cell announced by Gratzel et al., Switzerland, in 1991, and it is generally comprised of a photosensitive dye absorbing visible rays, metal oxide nano particles having wide band gap energy, a counter electrode which catalyses by platinum (Pt), and an electrolyte interposed between them. The DSSC has advantages of that the production cost is cheaper than existing silicon solar cells or compound semiconductor solar cells, the efficiency is higher than organic solar cells, and it is ecofriendly and can realize various colors.
Particularly, flexible DSSC is receiving more attention in that it can be used for self-charging a mobile phone or a next generation PC such as a wearable PC and the like, or can be utilized by attaching the same to clothes, a cap, an automotive glass, a building, and the like.
Meanwhile, the platinum catalyst needed for preparing the counter electrode of the DSSC is deposited by a sputtering method requiring a vacuum process at present. Furthermore, existing methods have prepared the counter electrode by calcinating a platinum compound at high temperature so as to prepare platinum nano-particles, or by putting a carbon-based material (carbon, carbon nano-tube, graphene) on a TCO substrate so as to use the same instead of the platinum catalyst.
However, these methods must use an expensive TCO electrode, and they need a vacuum process or a high temperature process. Furthermore, when only the carbon-based material is used, there is a problem of that the photoelectric efficiency of the solar cell becomes inferior to the cell using the platinum. Moreover, all of the processes must be carried out at low temperature in order to form the counter electrode directly on the flexible plastic substrate, and thus there is a problem of that the property of the electrode deteriorates.